This invention relates to mineral upgrading or concentration method involving the use of magnetic particles having hydrophobic surfaces, as extractants for minerals with hydrophobic surfaces or especially surfaces made hydrophobic by the use of the reagents normally used for air flotation concentration.
A considerable art has been developed to separate minerals from associated gangue using air bubbles. Typically a collecting reagent, such as sodium ethylxanthate, is added to an aqueous suspension of a mineral, for example chalcopyrite containing a silica gangue. The ethylxanthate ions are preferentially adsorbed by the chalcopyrite. If small air bubbles are then made to contact both silica and chalcopyrite particles, only the chalcopyrite particles adhere and they can then be floated to the surface of the suspension and separated by skimming the surface. The air bubbles are attached to the mineral by the surface tension developed in the ring where the mineral protrudes into the air bubbles. The air bubbles have buoyancy which counteracts the gravitational force on the particles of mineral thus allowing flotation to occur. In many instances the bubbles must be stabilised with frothing agents to maintain the bubble with particles on the surface for sufficient time to permit skimming of the floated mineral particles.